Internal combustion engines such as, for example, gasoline engines, diesel engines, and gaseous fuel powered engines, combust a mixture of air and fuel to produce a power output. The amount of air and fuel, and the ratio of air-to-fuel introduced into a combustion chamber of the engine can affect the power output, efficiency, and exhaust emissions of the engine. Typically, the amount of air introduced into the engine and the ratio of air-to-fuel is controlled by a number of different fluid handling components located in both the induction and exhaust systems of the engine.
For example, a turbocharger includes a turbine, driven by exhaust from the engine, which directly drives a compressor to pressurize air directed into the engine. Depending on an internal geometry setting of the turbine and compressor, more or less air will be compressed to a higher or lower pressure. In another example, a throttle valve located upstream or downstream of the compressor functions to selectively restrict the flow of air into the engine. A restrictive setting of the throttle valve limits the flow rate and/or pressure of compressed air entering the engine, while a nonrestrictive setting has little effect on the air entering the engine. The settings on the turbocharger and the throttle valve are generally independently controlled in response to one or more inputs.
Although the settings of the various fluid handling components are generally independently controlled, the effects of these settings may be interrelated. In other words, a change in the restriction of the throttle valve mentioned above can affect operation of the turbocharger and characteristics of the air pressurized by the turbocharger. Likewise, a change in the settings of the turbocharger can affect operation of the throttle valve and characteristics of the air restricted by the throttle valve. Because of this interconnected relationship, an instability within the fluid handling system can be generated when each component is independently controlled.
One attempt to minimize the likelihood of instability in a fluid handling system has been described in U.S. Pat. No. 6,817,173 (the '173 patent) issued to Paffrath et al. on Nov. 16, 2004. The '173 patent describes a method and apparatus for the simultaneous adjustment of an air intake stream and a secondary air stream directed into the exhaust system of an internal combustion engine. The secondary air stream is produced by a compressor driven by a turbine. The turbine is housed in a bypass duct arranged in parallel with a throttle valve associated with the air intake stream.
The amount of secondary air required to minimize instability is dependent upon a throttle valve setting. To create compensation for this, a control valve is connected through a connecting duct to the bypass duct to regulate a cross section of the bypass duct as a function of throttle valve opening. In the event of an opening of the throttle valve, the cross section of the bypass duct can be expanded simultaneously so that a pressure drop across the turbine, produced by throttle valve opening, does not produce system instabilities.
Although the system of the '173 patent may minimize system instabilities associated with two interrelated fluid handling components, it may be complex and costly. That is, in order to compensate for the effect of one component's operation on another, additional components (i.e., the control valve and connecting duct) are required. These additional components increase the control difficulty and expense of the system.
The disclosed fluid control system is directed to overcoming one or more of the problems set forth above.